Although any seizure may be frightening and cause for concern, experiencing one doesn’t mean you have epilepsy.

A person experiences a seizure when there is a sudden surge of abnormal electrical activity in their brain, caused by complex chemical changes in neurons or nerve cells. Seizures are not a disease — they are symptoms of many types of conditions that affect parts of the brain. In a seizure, you may experience symptoms of a temporary loss of consciousness or loss of awareness.

A seizure may also cause:

• Involuntary movements
• Disturbances in taste, vision, and hearing
• Changes in mood and cognitive function

Epilepsy is a disorder characterized by recurrent unpredictable (or unprovoked) seizures. For epilepsy to be considered as a diagnosis, a person must have had two or more unprovoked seizures more than 24 hours apart.

Triggers that may provoke seizures differ from person to person but can include:

• High fever
• Low blood sugar
• Alcohol withdrawal
• Brain injury
• Dehydration
• Missed meals
• Stress
• Sleep deprivation

These triggers may provoke a first seizure in people who are susceptible, but they may not have epilepsy. At the same time, such triggers can help bring on seizures in people with epilepsy.

Sixty-five million people have epilepsy worldwide, and more than 3 million have epilepsy in the United States, according to the Epilepsy Foundation.

The cause of epilepsy varies by age. In some people, epilepsy is a result of genetics or a change in the structure of the brain that brings on seizures. Three out of 10 children with autism spectrum disorder may have seizures. In young adults, seizures are also frequently seen in those with head injuries or tumors. In people over age 65, the most common cause of new-onset seizures is stroke. Six out of 10 seizures are idiopathic (without a known cause).

The International League Against Epilepsy has developed new terms to define seizure types in epilepsy:

• Generalized seizures affect groups of cells on both sides of the brain at the same time.
• Focal seizures affect a group of cells in one part of the brain.
• When the onset of a seizure is unknown, it’s called an unknown-onset seizure. A seizure may also be referred to as having an unknown onset if it is not witnessed by anyone, such as when someone living alone has a seizure at night.

The Difference Between Having Epilepsy and Having a Seizure

Several medical events or conditions are not epilepsy and may cause seizures.

Many people have a single or first seizure sometime in their life. They can be provoked or unprovoked. In most cases, single seizures do not recur and are not a sign of epilepsy unless the person has brain damage, a family history of epilepsy, or neurological abnormalities that cause seizures.

It’s not uncommon for children to have seizures during a high fever. These children are not usually treated with any kind of antiseizure medicine unless there are indications that the seizure may recur. These signs could include nervous system damage or a seizure that is especially prolonged or complicated.

Seizure Types Not Caused by Epilepsy

According to the National Institute of Neurological Disorders and Stroke, an estimated 5 percent to 20 percent of people diagnosed with epilepsy are believed to be misdiagnosed — they have actually experienced a nonepileptic seizure. Physically, these seizures look the same as those caused by epilepsy, but they are not linked with an excessive and abnormal electrical discharge in the brain.

Nonepileptic seizures can have a psychological cause. In clinical practice, they are referred to as psychogenic nonepileptic seizures (PNES). A history of trauma is one risk factor for PNES, and these seizures can be treated with cognitive behavioral therapy and other psychological treatments. A sign of PNES includes a lack of response to antiseizure drugs.

Medical conditions that cause nonepileptic seizures include:

• Narcolepsy — Sudden unreliable bouts of sleep
• Tourette syndrome — Repetitive involuntary tics
• Cardiac arrhythmia — Irregular heartbeats
• Eclampsia — Seizures that happen during pregnancy or shortly after giving birth
• Impaired liver or kidney function
• Abnormalities in the blood’s salt levels

If you experience a seizure, it is important to be evaluated by clinicians and a specialist in neurology. An electroencephalogram (EEG) can help detect if there are any abnormalities in brain waves, ideally 24 hours after a first seizure. The test may be useful in diagnosing epilepsy and in determining whether antiepileptic drugs will be beneficial.

Epilepsy and Recurrent Seizures

Epilepsy is a spectrum disorder, meaning that it has different causes, is marked by different seizure types, and its severity varies from person to person. There are many different types of epilepsy. Some people with epilepsy have very infrequent seizures. Others may experience seizures many times a day.

Most people diagnosed with epileptic seizures can control their symptoms with antiepileptic drugs, surgery, or lifestyle changes. However, as many as 30 percent to 49 percent of those with epilepsy continue to have recurrent seizures. Treatments and health care now available do not completely control epileptic seizures.

Most forms of epilepsy require lifelong treatment, but in some people, the seizures eventually go away. The chances of becoming seizure-free are better in those whose seizures start in childhood or have been effectively controlled by medication.

Some people who have epilepsy that can’t be controlled by drugs may undergo surgery to remove a small defined part of the brain or lesion where the seizures originate, and some may become seizure-free after surgery. Yet, such surgery is usually a last resort and is only tried in certain types of treatment-resistant epilepsy. The good news is that many people with epilepsy lead productive lives, and our understanding of seizures and their treatment is advancing rapidly.

Talk With Others Who Understand

MyEpilepsyTeam is the social network for people with epilepsy and their loved ones. On MyEpilepsyTeam, more than 108,000 members come together to ask questions, give advice, and share their stories with others who understand life with epilepsy.

Are you living with epilepsy? Share your experience in the comments below, or start a conversation by posting on your Activities page.